The present invention relates to devices for administering, injecting, delivering, infusing or dispensing a substance, and to methods of making and using such devices. More particularly, it relates to such a device for delivering a fluid product, wherein the device can be developed as an injection device for the injection of an adjustable dose of the product and can take the form of an injection pen, i.e. a compact injection device in pen-like form.
A large number of injection devices are known from the prior art for the dosed administering of medicaments or therapeutic agents such as insulin, growth hormones or osteoporosis drugs, which must be administered regularly. Such devices are on one hand intended to reliably and precisely deliver a dose which is able to be pre-set. On the other hand, they are intended to be user-friendly to a high degree. This applies all the more because they are generally operated by a person for self-administration.
The medicament can be housed in an exchangeable carpule (which also may be thought of and/or referred to as an ampoule, receptacle, container or reservoir), which is able to be inserted into a carpule holder. The latter can then be associated with or fastened to a housing of the injection device, e.g. by a screw connection or a bayonet connection. For distribution, a product stopper or piston in the carpule is pushed forward (toward the needle associated with the injection device) by a delivery arrangement with a delivery element in the form of a piston rod.
Compact, pen-shaped administering devices are known, in which the distribution takes place automatically after a first triggering (e.g. “power-assisted pens”). The dose in such devices is generally pre-set by a rotation of a dosing button. A drive is present in the device, e.g. a spring drive, which is tensioned on setting of the dose. The device is triggered by pressing a triggering arrangement, which can be identical to the dosing button. In so doing, the drive generates a drive movement, e.g. in the form of a rotary movement, which is converted into an advancing movement of the piston rod. In the case of a drive by a rotary movement, the piston rod may be constructed as a threaded rod on which a drive nut runs.
Injection pens are disclosed in DE-A 10 2004 063 644. These comprise a housing with a reservoir for the product and a delivery arrangement for delivering the product. The delivery arrangement is able to be driven by a drive arrangement. In one embodiment, the drive arrangement has a torsion spring and a coupling input member which is able to be driven rotatably thereby, which is able to be coupled with a coupling output member of the delivery arrangement. A triggering element, which at the same time also serves as a dosing member, is connected with the drive arrangement so that the drive arrangement is tensioned by a rotation of the triggering element. With this tensioning movement, the coupling which is formed by the coupling input member and the coupling output member is uncoupled, i.e. the tensioning movement is only transferred to the drive arrangement, but not to the delivery arrangement. On tensioning, the drive arrangement is prevented from turning back relative to the housing by a ratchet connection with an element which is fixed to the housing. By axial pressing in of the triggering element, firstly the connection between the triggering element and the drive arrangement is released, so that the triggering element can idle. Then the coupling is coupled and a connection is thus produced between the drive arrangement and the delivery arrangement. Finally, the ratchet connection between the drive arrangement and the housing is released, so that the drive arrangement can now carry out a rotation and can thereby drive the delivery arrangement.
A disadvantage in the preceding arrangement is that when the triggering element is not pressed in completely, only the connection between the triggering element and the drive arrangement is released, without, however, an administering being triggered. This is an undefined operating state. In this state, the user can turn the triggering element, which in fact at the same time also serves as dosing member, without this having any influence on the administering. Such an undefined state can lead to operating errors; such a state is therefore to be avoided. Furthermore, three operations or operational phases are necessary to trigger an administering: (a) releasing of the triggering and dosing element; (b) coupling of the coupling for the connecting of drive arrangement and delivery arrangement; and (c) releasing of the ratchet connection between drive arrangement and housing. None of these phases can be omitted without destroying the functionality of the device. In actual terms, even further connections are produced and released in the known injection device. Accordingly, this requires a relatively complicated structure.